Khi vận hành, máy móc bị sự cố cắt điện, bị nhiễu do sóng sét xâm nhập hoặc khi đang làm việc, sét đánh chết người là vấn nạn cần có biện pháp giải quyết. Bởi vậy, việc lightning protection có tầm quan trọng rất lớn để đảm bảo an toàn cho con người, máy móc, công trình và nhà ở.
1. Protection against direct lightning strikes on overhead lines
To protect against lightning on overhead lines, it is best to hang lightning conductors on the entire line. But this method is very expensive, so it is only used for 110 - 220 kV transmission lines. Overhead power transmission lines with voltage of 35kV or less are less protected by lightning protection wires of the whole line.
To enhance the lightning protection for these lines, it is possible to install lightning arresters or increase ceramic bowls in places with weak insulation, high overhanging poles, intersections with other lines, and sections to substations. Power networks that require very high continuity of power supply are best served by cable lines.
2. Protection against the harmful effects of lightning current
The lightning surge current penetrates into the overhead line, threatens the line's insulation, and discharges between phases (to earth) or between phases, causing a sudden power cut. It is necessary to equip lightning protection devices such as lightning protection valves... to cut down the peak amplitude and completely drain the lightning energy to the ground safely. This will slightly reduce the line insulation and ensure higher power supply continuity.
3. Grounding equipment
A serial lightning arrester is a device that conducts electricity to ground via a ground wire and a ground connection. The smaller our grounding resistance, the smaller the voltage at the lightning strike. If the special connection to the ground field cannot achieve the required number of values, then you can omit some position columns that are not connected to ground, but you must increase and strengthen the wire insulation to prevent the power from zooming through the position as well as the lines in the area. It is not recommended to ignore three consecutive positions on a wire.
4. Some points to pay attention to when protecting against direct lightning strikes
– A direct lightning protection system, or straight lightning protection system, usually consists of a lightning conductor, a lightning conductor, and a grounding system. Lightning poles can be made of steel pipes, placed independently or right on the equipment to be protected. To ensure long-term durability, the cross-section of the wire should not be less than 50 mm2, the grounding resistance of the earthing system must be less than 10Ω.
– In order to ensure good contact, the contact points need to be welded, if bolts are used to arrest them, they must create a good contact surface, have anti-rust plating, and have a cross section greater than twice the wire cross section. Conductors are painted or coated with zinc to prevent rust.
– The lightning protection network must be periodically checked, especially in the periods before the rainy season.
– In addition, it is necessary to pay attention to the necessary distance between the lightning rod and the protected object. In general, all protected objects must be completely within the protection range of the air-termination pole, but at the same time they must be a certain distance away from the air-termination pole.
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